The present invention relates to a method and system for conducting a shaking or vibration test for a structure. More specifically, the invention relates to a method and a system for conducting a vibration test which is particularly suitable for an object structure that is of such substantial size thereby rendering an excitation test for the whole structure difficult to perform. Also, the invention relates to a vibration response analyzing system suitable for analyzing vibration response of a structure including structures that are difficult to tested.
Clough, Ray W. "Dynamics of Structures", McGraw-Hill Kogakusha, Ltd., 1982, pp 575-578 describes excitation of a structure and equations of motion.
U.S. Pat. No. 4,953,074, entitled "Function-Distributed Control Apparatus", issued to Kametani et al., on Aug. 28, 1990 discloses a control apparatus for controlling automated machinery.
JP-A-60-13240 and JP-A-61-34438 disclose, respectively, a method for a response analysis and a vibration test with respect to a numeric model and a member.
K. Takahashi, "Japanese Activity on On-Line Testing" J. of Engineering Mechanics ASCE, Vol. 113, No. 7, 1987, pp 1014-1028, discloses analysis of the earthquake response by way of an on-line computer test.
Conventionally, evaluation of an earthquake or vibration response of a structure is performed by exciting the structure on a shaking table. However, when the structure significantly large, it is sometimes difficult to mount the actual structure on the shaking table due to capacity limitations of the shaking table. In such a case, evaluation of the earthquake response or vibration response is performed by performing an excitation test for a reduced structure which can be mounted on the shaking table, performing an excitation test only for the part of the structure, or performing an excitation test for a reduced part of the structure.
However, the former method has difficulty securely satisfying a law of similarity upon establishing the reduced structure, or so forth. On the other hand, in the latter method, there is difficulty or even an impossibility of producing highly precise excitation since the exciting vibration applied to the object structure of excitation is per se associated with the response of the structure to be excited, which makes it difficult to achieve accurate evaluation of the earthquake or vibration response.
In view of these problems, there is another approach for establishing a vibration testing method, in which only a part of the structure, i.e. a member, is excited and remaining members are established as a numerical model, a vibration response at a boundary is calculated by means of a digital computer, the member as the numerical model is excited and further evaluation of the numerical model is performed using a reaction at the boundary.
The vibration testing methods, in which the part of the structure, member or the reduced structure is excited and calculation of response for other parts is performed by means of the digital computer with establishing the numerical model for those parts, have been disclosed in the above-identified references JP-A-60-13240 and JP-A-61-34438.
It should be noted that conventional vibration response analyzing system for the structure performs calculation by establishing the numerical model of the overall structure as the object for evaluation of the vibration response, by way of a finite element method, for example.
In the method disclosed in JP-A-60-13240 and JP-A-61-34438, a displacement is provided by means of an actuator expanding a time axis. Therefore, it is possible to accurately measure the reaction only depending upon the displacement, and cannot evaluate reaction depending upon a velocity, such as viscosity damping force. Furthermore, since the time axis is expanded, it requires several hours for evaluation of a phenomenon corresponding to an earthquake response in the order of several tens of seconds.
In addition, in the latter publication, the reaction depending upon an acceleration is evaluated by providing an actuator applying a load corresponding to an inertia force. However, since the load by the actuator is applied at a single point, it becomes inaccurate for a distributed load which cannot be modeled into concentrated mass system.
The applicant has made an attempt to perform vibration test method in real time with respect to an equipment to be stationarily installed, in order to solve the problems as set forth above. Through the attempt, it has been found that it is difficult to apply the attempted method for the evaluation of stress due to relative displacements or so forth at a plurality of points, since the object to be excited is oscillated or vibrated on the shaking table.
Furthermore, means for effectively processing calculated values and measure values have not been considered in the prior art.